Assessment of both IDEXX Angio Detect on bronchoalveolar lavage fluid and Angiostrongylus vasorum quantitative polymerase chain reaction on EDTA blood in dogs that tested negative for IDEXX Angio Detect on EDTA blood

Angiostrongylosis due to Angiostrongylus vasorum (A. vasorum) infection is a commonly encountered parasitic lung disease in dogs. On some occasions, the traditionally used in-clinic antigen test IDEXX Angio Detect performed on EDTA blood could lead to false negative results. Due to intermittent shedding of A. vasorum larvae in faeces, the sensitivity of faecal analysis by Baermann method is also imperfect. Accordingly, definitive diagnosis of angiostrongylosis sometimes requires polymerase chain reaction (PCR) for A. vasorum on a bronchoalveolar lavage fluid (BALF) sample obtained by bronchoscopy under general anaesthesia. The aims of this study were to assess the diagnostic utility of both (1) in-clinic IDEXX Angio Detect on BALF samples and (2) laboratory quantitative PCR for A. vasorum on EDTA blood sample in dogs that tested negative on blood IDEXX Angio Detect. Stored BALF and EDTA blood from 6 dogs (median age 4 years, range: 1-9) that tested negative on blood IDEXX Angio Detect, but were diagnosed with angiostrongylosis based on positive quantitative PCR on BALF were retrospectively used for the purpose of this study. All IDEXX Angio Detect performed on BALF (n=5, leftover BALF from dog n3 unavailable) were negative, whereas duplicate quantitative PCR on EDTA blood were positive in 2 out of 5 dogs (dogs n1 and n3, leftover EDTA blood from dog n5 unavailable). When positive, blood PCR results had high cycle threshold values (mean 37.0 ± 0.9) suggesting initial low template DNA in the sample. Results of this study demonstrated that IDEXX Angio Detect on BALF samples is of no added diagnostic value in dogs that tested negative on EDTA blood. However, quantitative PCR for A. vasorum on peripheral EDTA blood could be used for angiostrongylosis diagnosis in a subset of dogs that tested negative on blood IDEXX Angio Detect. This is of particular relevance in dogs that are clinically unstable and at risk of general anaesthesia for bronchoscopy and BALF sampling. Further larger study is advised to provide specific diagnostic accuracy characteristics for A. vasorum quantitative PCR on EDTA blood